[Li Jianliang]

Originally Posted by Jan-Poo

So that clock should have been changed as well. But Natsuhi's door was locked so you'd have to suspect a servant to be involved.

It makes sense, because the guestroom on the first floor was unlocked as well, and someone must've unlocked Natsuhi's room to put the Autumn card there, too. It's always the servants, baaah. XD

Spoiler for Observations and theories concerning Hideyoshi's murder:

4. Murder of Hideyoshi in the first guestroom on the first floor of the mansion

This mystery feels like it's almost separate from the other three, since it took place after 1PM on the second day where Natsuhi 'witnessed' the entire thing. Assuming that Natsuhi wasn't hallucinating about the details she gives you, the player, then the circumstances were that Hideyoshi entered the guestroom after 1PM and soon noticed someone else in the room (other than Natsuhi hiding in the closet, who Hideyoshi never noticed). After a brief struggle, the culprit stabbed Hideyoshi in the back. Eva attempted to enter the room but is stopped by the chained door, so she left to grab other people, but by the time she returned with them and a chain-cutter, Hideyoshi was already dead on the bed.

Question: Was Hideyoshi the target?
Did the culprit want Hideyoshi dead and just tailed him when he split away from the rest of the group? Or did the culprit want to kill anyone separated from the group? Or was the culprit originally aiming for Natsuhi in the closet and had to switch targets when Hideyoshi entered the room, before the culprit could get to Natsuhi? I'm guessing, it seems more likely that Natsuhi was the intended target, since the culprit (assuming he or she was working in cahoots with "the man from 19 years ago") knew Natsuhi would be alone. Who knew Hideyoshi would want to go sob about George's death in solitude?

Question: How did the culprit hide in the room?
The guestroom is normally locked since it's rarely used. It was already unlocked when Natsuhi entered and hid herself in the closet. She heard Hideyoshi entering, too, but she did not hear anyone else entering, which suggests that the killer was already in the room before Natsuhi entered, also hidden somewhere in the room. However, by Erika's observations, it doesn't sound like there was much furniture in the room to hide in or behind, except for the closet.
One theory, the culprit was hiding under the bed or the like. If that was the case, then Erika would've noted the bed in her observation, and the only thing she deemed able to hide an entire person was the closet.
Another theory, the man-sized closet had two or three vertical compartments; the culprit hid in one and Natsuhi hid in another. However, given that the closet couldn't be locked from either side, it would be too much of a gamble for the culprit.
Another theory, the culprit was hiding in some non-blind spot place, such as behind the door, etc. This feels too absurd, since Hideyoshi would've noticed the person.

Question: So, if the culprit wasn't in the room to start with, how did the culprit get in?
To argue that the culprit entered the room after Natsuhi, or even after Hideyoshi, then I have to hypothesize that Natsuhi, with her frantic thinking and raging headache, could not hear the quietest of sounds. Perhaps the culprit was indeed able to sneak into the room after Natsuhi. After Hideyoshi, it would've been more difficult, because Hideyoshi put up the door chain (Natsuhi did not). Just think, if Natsuhi put up the door chain after herself, maybe Hideyoshi's murder could've been prevented? But I digress.
If the culprit entered right after Natsuhi, I doubt Hideyoshi would've overlooked another person in the room who wasn't in the closet. So let's say the culprit entered the room after Hideyoshi did. It couldn't have been through the window, because that was locked after the inside (Hideyoshi went to close the window shutters right after he entered), and without any other method of entry, it must've been through the door, which was chained. The chain definitely wasn't broken, because when Eva tried to open the door later, it held strong. My best theory here is that the culprit, knowing someone (Natsuhi) would be in the guestroom at that hour, switched out the chain for a slightly longer one beforehand, a chain long enough for someone to reach a hand in and undo the chain lock from the outside. Since Hideyoshi was distraught and chained the door while the door was fully closed, it was probably difficult for him to discern that the chain was a little longer than usual. Also, it's a guestroom, a room that he probably doesn't normally use since he's a family member and he doesn't live in the mansion to thoroughly memorize what every single room in the mansion is like. Hideyoshi was also sobbing face-down in the bed, thereby muffling his senses and making it possible for someone to unchain (and re-chain) the door and enter very quietly. When Eva later tried to enter the room and ran into the chain, she heard Hideyoshi making death moans and may have panicked so much that she also failed to recognize that the chain was longer than usual. Natsuhi heard Eva rapidly and repeatedly open and slam the door in a vain effort to break the chain, and it would be tough to discern the length of chain while it is in motion like that.

Question: Who's the culprit?
Hideyoshi yelled, "Who's there?!" which hints that the culprit is someone who he couldn't recognize. Since there weren't any strangers on the island, it suggests that the culprit was wearing a mask or disguise of some sort. Why would the culprit do that? Also, given that the culprit was able to overpower Hideyoshi and kill him, it is unlikely someone of weaker physique did it solo.
Another point, Natsuhi only heard Eva attempting to enter the room. What if that was all faked for people who happened to be within earshot of the room? Since Natsuhi never saw the events, it is possible that Eva was or was working with the culprit to kill Hideyoshi. However that goes against the central theme of 'love' in the game; why would Eva want to kill her dear husband?

Question: How did the culprit leave the room?
The same as method of entry, the culprit only could've left through the door. Natsuhi didn't hear anyone leaving and believed the culprit was still in the room after Hideyoshi's murder and Eva leaving to get other people. If the culprit only entered the room and never left, is it possible that the culprit hid in a place like behind the door and simply joined the group that entered later? People may have been too distracted by Hideyoshi's body and Eva's screaming and crying to notice. If Natsuhi heard wrong, then in the same way the culprit was able to soundlessly enter the room, the culprit could've quietly slipped out, re-chained the door from the outside, and joined the group of people in the drawing (reception) room. If the culprit was Eva or working with her, then it is possible that the culprit left during Eva's door-banging ruckus.